Conventionally, in a process for semiconductor manufacturing, perfluorocarbon (PFC) gas has been used as an etching gas and a cleaning gas. However, it is considered that this PFC is one of the sources of causing global warming because this PFC has a long life in the air and a very high global warming potential. Therefore, the development of alternative gases and the development of a new etching system have been desired.
When the PFC gas is plasmanized, plural kinds of radicals such as CF radical, CF2 radical and CF3 radical are present in this plasma. Of these radicals, it is known that CF3 radical can attain a higher etching rate in a plasma etching process of a silicon oxide film (SiO2) as compared with other radicals (referred to a nonpatent literature 1). On this account, it is an important object to generate CF3 radical selectively from the viewpoint of the efficiency of the etching process. Further, conventional plasma etching processes have a problem such that an etching substrate consisting essentially of SiO2 and a resist has low etching selectivity to a SiO2 film. Therefore, the development of a plasma etching process having high etching selectivity to the SiO2 film has also been desired.
However, in the conventional plasma etching processes using PFC gas, it is difficult to generate a specific radical selectively, and further it is impossible to improve the etching selectivity to the SiO2 film. Under the circumstances, the development on a new radical generating method for generating CF3 radical selectively and etching system using this method has been desired.
Patent literature 1 discloses an etching method and an etching apparatus using a carbon material as an upper electrode (application electrode). The etching method comprises etching an AlCu alloy film using chlorine radical as an etching source. The carbon species generated from the carbon material by applying a high frequency voltage to an application electrode are used to scavenge excess amount of chlorine radical (etching species) present in TiN/Ti etching after the completion of etching the AlCu alloy film. That is, Patent document 1 fails to disclose and suggest generation of an etching species such as CF3 radical using a carbon species generated from the carbon material. Further, the document fails to disclose that a specific radical can be selectively generated by regulating the voltage applied to an application electrode.    Patent document 1: JP-A-11(1999)-145118    Nonpatent literature 1: T. Shibano, N. Fujiwara, M. Hirayama, H. Nagata and K. Demizu, Appl. Phys. Lett. 63, 2336 (1993)